EMS Technologies Canada Ltd. HSD-400 Manuale Utente

(1) Power Requirements

The aircraft power supply provides power to the HSD-400 terminal. This power supply 
must be +28 V dc nominal for model 1252-A-3200. For HSD-400 terminal model 
1252-A-3100, the power supply must be at 115 V ac, 400 Hz (nominal). 

(2) Ground Requirements

Improper grounding can potentially lead to ground loops and induced Electromagnetic 
Interference (EMI) or Radio Frequency Interference (RFI). When installing an 
HSD-400 terminal, follow standard grounding practices for both chassis and cabling 
shields. Refer to section D on page 3–4 for chassis and tray grounding instructions.

(3) Cable Shielding and Termination 

The preferred method of cable shield termination is in accordance with NEMA WC 
27500:2000 and ARINC 741. ARINC Report 413A - Guidance for Aircraft Electrical 
Power Utilization and Transient Protection provides more detailed information in 
Attachment 3-2, Wire Shielding and Grounding Requirements and in Appendix 7.

Unless otherwise stated, all cable shields must be connected to the closest aircraft 
ground at both ends of the cable and on both sides on any production break in the 
cable. Where applicable, terminate shields with connectors via the backshell or via a 
pigtail with a suitable termination to the closest aircraft ground. 

General aviation cable-routing guidelines apply. See Table 3-2 for detailed 
information.

Note: Typically, Ethernet and ISDN cables have multiple shields; terminate each 

shield separately.

Power Lines

Single conductor, 

stranded

N/A

N/A

N/A

Digital Control

Twisted pair, 

stranded

Yes

85%

Serial Data

Twisted pair, 

stranded

Yes

85%

Ethernet Data

Twisted pair, 

stranded

Yes

85%

ISDN Data

Twisted pair, 

stranded

Yes

85%

Discrete Lines

Single conductor, 

stranded

N/A

N/A

N/A